09-28-2021, 05:21 PM
This post is copied from the FaceBook group with a few addendums from the comments. Original post credited to Steve M.
I have had problems ranging from rough running, petrol leaking over the garage floor and cylinders that are so full of fuel that the bike does not turn over due to "hydraulic lock" all depending on how long the bike is left for. Clearly there was a problem with fuel passing through the fuel tap (petcock), even in the off position, and then past the float valves, that also should close off the supply.
![[Image: Flooded_Carbs.jpg]](https://gaijinagain.com/wp-content/uploads/2021/09/Flooded_Carbs.jpg)
First I tried a carburetor rebuild with new float needles and a good clean . Second I put a new diaphragm in the vacuum operated valve in the fuel tap (petcock). I even tried replacing the fuel pump after reading every single carburetor or fuel related comment ever made on the SRV250 forum!!! However I could not find out why the fuel issue continued.
But here is the solution. To the right hand side of the fuel tap (petcock) is an extra fuel line marked "return" which is connected to one of the carburetors. The fuel appears to go from the tank, to the fuel tap (petcock), to the vacuum operated valve, to the pump, to carburetor 1, to carburetor 2 then back to the fuel tap (petcock). Inside this return connection on the fuel tap (petcock) is a spring and a valve that while the engine is running and fuel flowing has pressure that opens the valve and allows fuel to return to the fuel tap (petcock). When the engine stops the spring closes the valve. This is similar to the vacuum operated valve on the other side of the fuel tap (petcock) in that it is designed to stop fuel leaking into the carburetors or cylinders when the engine is not running.
![[Image: Petcock.jpg]](https://gaijinagain.com/wp-content/uploads/2021/09/Petcock.jpg)
![[Image: Spring_Valve.jpg]](https://gaijinagain.com/wp-content/uploads/2021/09/Spring_Valve.jpg)
So many forums and workshop manuals refer to the diaphragm operated valve as being the cause of all these problems but no other bike has the complicated system that the SRV250 has in that there is an additional valve on the other side of the fuel tap (petcock). I removed it and inside it was corroded and jammed in the open position allowing fuel to drain, via gravity, from the tank into one of the carburetors bypassing all other valves designed to stop fuel leaking. A good clean of the valve seat & a new tiny oil seal on the valve has now cured the problem. Perhaps this highly unusual valve that is not mention in workshop manuals, forums etc could also be a cause of other members fuel related problems that they have not been able to resolve by normal well known methods. I know this has been a long explanation of this issue but this is a very rare return valve that nobody other than SRV250 owners have and all our bikes are now old and therefore likely to have these corroded malfunctioning valves.
I have had problems ranging from rough running, petrol leaking over the garage floor and cylinders that are so full of fuel that the bike does not turn over due to "hydraulic lock" all depending on how long the bike is left for. Clearly there was a problem with fuel passing through the fuel tap (petcock), even in the off position, and then past the float valves, that also should close off the supply.
First I tried a carburetor rebuild with new float needles and a good clean . Second I put a new diaphragm in the vacuum operated valve in the fuel tap (petcock). I even tried replacing the fuel pump after reading every single carburetor or fuel related comment ever made on the SRV250 forum!!! However I could not find out why the fuel issue continued.
But here is the solution. To the right hand side of the fuel tap (petcock) is an extra fuel line marked "return" which is connected to one of the carburetors. The fuel appears to go from the tank, to the fuel tap (petcock), to the vacuum operated valve, to the pump, to carburetor 1, to carburetor 2 then back to the fuel tap (petcock). Inside this return connection on the fuel tap (petcock) is a spring and a valve that while the engine is running and fuel flowing has pressure that opens the valve and allows fuel to return to the fuel tap (petcock). When the engine stops the spring closes the valve. This is similar to the vacuum operated valve on the other side of the fuel tap (petcock) in that it is designed to stop fuel leaking into the carburetors or cylinders when the engine is not running.
So many forums and workshop manuals refer to the diaphragm operated valve as being the cause of all these problems but no other bike has the complicated system that the SRV250 has in that there is an additional valve on the other side of the fuel tap (petcock). I removed it and inside it was corroded and jammed in the open position allowing fuel to drain, via gravity, from the tank into one of the carburetors bypassing all other valves designed to stop fuel leaking. A good clean of the valve seat & a new tiny oil seal on the valve has now cured the problem. Perhaps this highly unusual valve that is not mention in workshop manuals, forums etc could also be a cause of other members fuel related problems that they have not been able to resolve by normal well known methods. I know this has been a long explanation of this issue but this is a very rare return valve that nobody other than SRV250 owners have and all our bikes are now old and therefore likely to have these corroded malfunctioning valves.
My Bikes: SRV250, Ninja 250R
